Mental maps. Maps with edges. And for Auden, for so many of us, it's the edges of the maps that fascinate...

Map-making had never been a precise art on the Discworld. People tended to start off with good intentions and then get so carried away with the spouting whales, monsters, waves and other twiddly bits of cartographic furniture that the often forgot to put the boring mountains and rivers in at all.

They were maps that lived, maps that one could study, frown over, and add to; maps, in short, that really meant something.

You can't map a sense of humor. Anyway, what is a fantasy map but a space beyond which There Be Dragons? On the Discworld we know that There Be Dragons Everywhere. They might not all have scales and forked tongues, but they Be Here all right, grinning and jostling and trying to sell you souvenirs.

It was ... disconcerting to examine your charts before a proposed flight only to find that in many cases the bulk of the terrain over which you had to fly was bluntly marked: 'UNSURVEYED.'

It was as if the mapmakers had said, 'We are aware that between this spot and that one, there are several hundred thousands of acres, but until you make a forced landing there, we won't know whether it is mud, desert, or jungle -- and the chances are we won't know then!

It seemed that the printers of the African maps had a slightly malicious habit of including, in large letters, the names of towns, junctions, and villages which, while most of them did exist in fact, as a group of thatched huts may exist or a water hole, they were usually so inconsequential as completely to escape discovery from the cockpit.